There are several things a person should not do. Some of these things are mate with a close sibling, snort Cocaine cut with rat poison and play a game called Legendary. That's because doing acts such as these come with serious repercussions. These consequences would be conceiving some sort of deformed mutant baby, brain damage or death.
The only way to enjoy Legendary is to gather up Tom Servo, Crowe T. Robot and Mike Nelson of Mystery Science Theatre 3000 fame and have them crack jokes as you play it.